1. Field of the Invention
The present invention relates to a turbomolecular pump including a housing and stator and rotor disc arranged in the housing.
2. Description of the Prior Act
Active pumping elements of a turbomolecular pump consist of rotor and stator discs provided with vanes and arranged alternatively one behind the other. The rotor and stator discs have each an inner carrier ring on an outer side of which a vane is provided. The vanes of the rotor discs, which rotate with a high speed, produce, together with the stator vanes, a pumping effect. Spacer rings are arranged between the rotor discs at their outer circumference, separating the rotor discs from each other by a distance that insures a contact-free rotation of the rotor discs. Stator discs, together with spacer rings, form a stator which is centered by the housing inner wall, with the stator discs and spacer rings being, e.g., pressed to each other axially with springs, whereby the stator discs and the spacer rings form a rigid connection.
This conventional design of a turbomolecular pump has many drawbacks, the major one being the necessity to produce a large number of separate parts. This result in high manufacturing costs and increased assembly time and adversely affects repair and maintenance works. The need to maintain narrow tolerances, which are necessary for the reliable operation of the turbomolecular pump, together with a large number of parts, results in extremely high expenses. Further, radial centering and axial fixation of the stator discs require additional adjustment which, likewise, contributes to increased manufacturing costs.
German Publication DE OS 22 18 615 discloses a turbomolecular pump formed of one stator and one rotor arranged in the pump housing, with the stator being formed of two cylindrical shells. The drawback of this pump consists in that the stator should be mounted in a separate housing with a cumbersome radial centering and axial adjustment. This is accompanied by increased manufacturing costs and increased assembly time and involves expensive maintenance works. Unavoidable gaps between the stator and the housing results in disturbing return flows. Further, insufficient removal of heat, which is produced during the pump operation, from the pump adversely affects the operation of the pump.
The German Publication DE 07 51 297 discloses a turbomolecular pump the stator of which is also formed of two parts. This pump does not have a housing. Therefore, the stator is directly submerged into a reservoir. If a housing is provided, the above-mentioned drawbacks result.
Accordingly, an object of the present invention is to provide a turbomolecular pump a number of components of which is substantially reduced in comparison with conventional turbomolecular pumps.
Another object of the present invention is to produce a turbomolecular pump that can be produced with substantially reduced manufacturing costs in a shorter time and maintenance of which is substantially simplified.
A further object of the present invention is to produce a turbomolecular pump with improved removal of heat generated during the pump operation.
A still further object of the present invention is to produce a turbomolecular pump in which the return or backward flow is substantially reduced.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by forming the cylindrical housing of at least two housing parts separated along a cylinder axis, with each part being formed, together with respective separated sections of the stator discs, as a one-piece unit.
The present invention permits to substantially reduce the number of components of a turbomolecular pump. Spacer rings are eliminated. This simplifies manufacturing and reduces assembly time. Also, the maintenance works are simplified and reduced. Obtaining of necessary tolerances is substantially facilitated in view of a smaller number of pump components. The radial centering and axial fixing is obtained upon manufacturing of the housing parts and do not require any further adjustment.
Inner leakage, which was caused by gaps between numerous stator elements, is eliminated, whereby disturbing backflows in these regions are eliminated to a most possible extent. The removal of heat, which is generated during the pump operation, is substantially improved due to the compact design of the housing and to the elimination of transitional regions which in conventional pumps hinder arrangement of the heat conductors for heat removal. In addition, provision of cooling or heating elements in the region of stator elements permits to provide for an operational temperature regulation of the entire construction, in particular, of pump active parts in dependence on the operational condition of the pump.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.